Switching mechanism



Sept. 9, 1941. F. D. Jol-:sTlNG Erm.

SWITCHING MECHANISM Filed Aug. 12, 1938 o@ inmntors Tiges @auditing Patented Sept. 9, 1941 swrroHING MEonANTsM Frederick D. Joesting, Chicago, Ill., and Leslie H. Miller, Minneapolis, Minn., assgnnrs to Minneapolis-Honeywell Reg ulator Company, Minneapolis, Minn., a corporation of Delaware Application August 12, 1938, Serial No. 224,530

(Cl. 20o-138) 13 Claims.

This invention relates generally to the art of electric switching and more particularly to a plurality of switches which are operated in a certain order by a condition responsive device.

In certain types of oil burnecontrol systems, such for example as the system disclosed in the patent to Kriechbaum 1,921,196, it is desirable to provide a combustion responsive switch which will close one circuit on a rise in temperature and will close a second circuit on a fall in temperature. Furthermore these circuits must be overlappingly controlled in one direction and nonoverlappingly controlled in the other; that is, as the temperature rises one circuit must be made before the other circuit is broken, and on a fall in temperature the one circuit must be broken before the other circuit is made.

It is a prime object of this invention to provide an automatic switching mechanism which will meet the above requirements.

A further object is to provide a switching mechanism which will produce the desired operating sequence with a minimum amount of force and movement.

A further object is to provide a switch mechanism of the above type which is operated by a temperature responsive device through a slip friction connection so that the switches will be operated on a change in temperature rather than onA any absolute temperature, and one of the switches will be operated substantially immediately upon a change in temperature in either direction.

A further object is to provide a switching mechanism having two sets of contacts wherein engagement of one set will cause disengagement of the other set on a change in the condition value in one direction, and wherein a latch is provided to prevent engagement oi' the other set until after the disengagement of the rst set on an opposite change in the condition value.

A still further object of the invention is to provide adjusting means in a switching mechanism of the above type so that the timing of the various switching operations may be predetermined. Although this switching mechanism has been mentioned in connectionwith anoil burner control system it is obvious that it may have many other uses4 and it is therefore intended that this application be directed to the switching mechanism p er se rather, .than its use #n any particular system. l

For a better understanding ci the device, reference is made to the following specification in conjunction with the accompanying drawing, in which Figure 1 illustrates the switch mechanism of our invention with the parts in cold position,

Figure 2 shows an intermediate position oi the switch on a rising temperature,

Figure 3 shows the switch in hot position, and

Figure 4 shows an intermediate position of the switch on a falling tempera-ture.

The switch mechanism of our invention is mounted on an insulating panel II which carries a pin I2 about which lever I3 is adapted to rotate. Diagrammatically illustrated at I5 is a thermostatic element having a iixed end I6 and a free end I1 which is connected to an operating rod I8. 'I'he rod I8 passes between and is guided by a pair of rollers I9. An element 20 is provided with a transverse hole (not shown) through which the operating rod I8 extends in a manner to produce a slip friction connection between the two. The element 20 is provided with a pin 2I which extends through an elongated slot 22 in the lower part of the lever I3. Ihe lower end 23 of the lever I3 is adapted to oscillate between a pair of adjustable stops 24 and 25 which are screw-threadedly mounted in posts 26 and 2l, respectively. On variations in temperature, the thermostat I5 moves the operating rod I3 back and forth carrying with it the friction element 20 which in turn causes rotation of the lever I3. l The stops 2l and 25 limit the movement of the lever I3 and hence the friction element 2U, and on further deilection of the thermostat I5, the operating rod I8 will slip with respect to the friction element 20. The purpose of this arrangement is to cause the lever I3 to be actuated on a change hi temperature rather than have its movement dependent upon any particular degree of temperature.

A lever 30 is rotatably mounted by means of two depending ears 3| and 32 on a pin 33 which is suitably secured to the base Il. The ear 32 is provided with a tapered slot 3l in which is inserted one `end of a metal piece 35 which is carried by the upper end 36 of the lever I3. Rotation of the lever I3 will therefore produce a rotation of the lever 30 through the engagement of the metal piece 35 with the slot 3|.

Mounted on the upper side of the lever 30 is an v insulating strip 40 on whichfrests a flexible strip 4I having two electrical contacts 42 and 43 mounted on the opposite ends thereof. The strip 4I is provided with an oversize hole through which extends the stem of a screvr Il, which screw-threadedly engages the lever 3ll and clamps the strip 4I and insulation l0 to the lever ible strip 5I biases the contact arm 52 downwardly toward flever 3U. The Varm 52 is provided with a pair of `holes in which are inserted insulating bushings 53 and 54 having metal inserts in which are screw-threaded theadjustable contacts 56 and 5l. The contacts 56 and 57 are so positioned as to cooperate with the contacts 42 and 43 mounted on the flexible strip di.

The lever 36 is provided with a pair of ears, one of which is shown at 60 and between which is mounted a pin 6I which rotatably carries a latch generally indicated at 62. Spring member 63 is coiled about the pin 6I and one end engages beneath the lever 30 and the other end engages the latch 62 to bias the latch for rotation in a counter-clockwise direction with respect to the lever 30.

The latch 62 is provided with an arm 65 which is adapted to cooperate with the end 66 of the lever 52 in a manner to be described later on in detail, and an arm 6l which is adapted to cooperate with a stop 68 which is screw-threadedly mounted in post 69 which is in turn secured to the base II.

In considering the operation of the switch mechanism, it is assumed that the thermostat I5 flexes toward the left as shown ln Figure 1 on a fall in temperature and towards the right on a rise in temperature. Figure 1, therefore, discloses the parts in their cold position at which will move towards the left carrying with it the friction element 26 which will produce a clockwise rotation of the lever I3. The lever I3 will cause la counter-clockwise rotation of the leverA 36 and in doing so will raise the latch 62 and as the arm 65 is carried beneath the end 66 of the lever 52, it will raise the lever 52 against the force exerted by the resilient strip 5I 'while contact i2 is moving downwardly and cause a separation of the contacts 42 and` 56. This condition is illustrated in Figure 4.

On a further decrease in temperature, th lever 30 will be further rotated in a counterclockwise direction and the arm 61 on the latch 62 will eventually strike the adjustable stop 68 which will cause the latch 62 to rotate in a clockwise direction about the pin 6I causing the arm 65 to move towards the right as viewed in Figure 4 and release the arm 52, at which time the Y v mostat I5 will not affect the switch mechanism time the contacts 43 and 51 are closed. It is understood that the fiexible strip 4I and the adjustable contacts 56 and 51 are each individually connected to conductors for connection with suitable outside circuits. On an increase in temperature at the thermostat I5, it will start to iiex toward the right carrying with it the friction element 20 which produces a counter-clockwise rotation of the lever I3. By means of the metal piece'35, the lever I3 ,produces a clockwise rotation of the lever 30 which will eventually bring the contacts 42 and 56 into engagement while the contacts 43 and 51 remain in engagement. This condition is illustrated in Figure 2. Up to this point, the latch 62 has not entered into the operation of the switch mechanism. On a further rise in temperature, the 'lever 36 will continue to nrotate in a clockwise direction and through its engagement with the lever 52 through the contacts 42 and 56 will cause the lever 52 to l rotate in a counter-clockwise direction against the bias of the flexible strip 5I causing a separation of the contacts 43 and 51. Just before the end 23 of the lever I3 strikes the vadjustable stop 24, as shown in Figure 3, it will be noted that ythe arm.65 on the latch 62 has dropped oil' the rod I8 will slipthrough the hole in the friction element 20. Y,

Immediately upon a decrease in the temperature at the thermostat I5, the operating rod I8 but the friction element will permit a further deiiection of the thermostat. ',Thus the,` parts havev been returned to their cold position which is illustrated in Fig. 1 and thejabove cycle may be repeatedindenitely.

It will be seen therefore that a switch mechanism has been provided which in its cold position has one set of switch contacts closed and which on a rise in temperature iirst closes a second set of switch contacts and then breaks the rst set oi switch contacts, the second set oi switch contacts being closed with the mechanism in its hot position, and which on a decrease in temperature rst breaks the second set of switch contacts and then remakes the iirst set of switch contacts which remain closed in the cold position of the mechanism. In other words, a pairof switches are provided which aremechanicallxrl actuated from a thermostat to provide for` an overlap on heating and not on cooling.

It will be appreciated that various adiits have been provided so that the time between Athe various operations may be nicely adjusted. For instance, the switch contacts 66 and 61 are both adjustably mounted on the lever 62 and the stop 68 is adjustably mounted in the post 69. If the stop 68 is lowered, the time required 'for the switch 43, 51 to be closed following the openingv of the switch 42, 661wi11 be reduced, and conversely, it the stop is raised this time will be increased. Also if the contact screw 56 is raised, the time be-` tween the closing of the switch 43, 51 and the closing of the switch 42, 56 is increased. Thus by these adjustments the-timing of the various switch operations may be changed. Also the stops 24 and i5c are made adjustable so that the movement of the lever I 3 may be limited'to the properrange to permit the proper actuation of the switch mechanism without necessitating any -unnecessary movement o! the lever. For instance, the stop 25 must be so positioned as 't0 permit they lever I3' to'move sumciently vfar to move theI arm from beneath the end 66 ofthe lever 52 to permit the contacts V43 and 51' to engage. On the other hand, the stop 24 must be scl positioned vthat the lever I3 can be moved far N tments enough to permit the arm 65 to drop off the end 66 and latch itselfbeneath the lever 52. If sui'- iicient movement is not obtained to move the latch 62 in this manner, the mechanism will become inoperative for the purpose for which it was devised. l Also by moving the stop 24 towards the right the amount of temperature drop required to open the contacts 42, 56 may be adjusted.

There are two decided advantages in this switch actuating mechanism aside from the timing and sequence features. One is that as the contacts are actuated there is a slight sliding movement with respect to the contacts so that their Surfaces will always be kept clean. Another feature is that the contacts will always be made with a good firm pressure. The contacts 43 and 51 are made by the lever 52 dropping off the arm 65 which will assure a good firm contact and the 'lever 52 -is raised by the coaction between the contacts 42 and 56 so that a good firm contact pressure between these contacts is also assured. A third and perhaps the most important feature is that the proper sequence of switch operations is obtained by using a slight force which operates through only a small distance. Thus the force required to move the rod I8 is small and need operate only through the distance determined by the stops 24 and 25.

Certain changes and modifications in this invention will undoubtedly occur to those who are skilled in the art and it is therefore understood that we intend to be limited by the scope of the appended claims rather than by the specific embodiment disclosed.

We claim as our invention:

1. A switching mechanism comprising a first movable member, a second movable member, a first switch formed by a first contact on said first member and a rst contact on said second member, a second switch formed by a second contact on said first member and a second contact on said second member, means for moving said first member, means on said rst member for moving said second member, and a stationary element causing said latter means to disengage said second member.

2. In combination, a switch arm, a pair of con- Y tacts mounted for cooperation with said switch arm, a condition responsive device for moving said arm in one direction to first engage one contact and then separate from the other, and means carried by said switch arm for holding said other contact out of engagement withv said switch arm until after the switch arm has separated from said one contact on movement ofl said switch arm in the opposite direction.

3. In a device of the character described comprising in combination, a switch arm, a movable member, a pair of contacts carried by said movable member, a condition responsive device for moving said arm in one direction to rst engage one contact and then separate from the other, means on said arm engaging and moving said movable member as said condition responsive device moves said switch arm in the opposite direction so as to prevent said switch arm from engaging said other contact, and means for disengaging said first mentioned means from said movable member after said switch arm has dis engaged said one contact to permit it to engage said other contact. j

4. In a deviceof the character described comprising in combination, a switch arm, a movable merriber, a lpair of contacts carried by said movable memben'a conditionresponsive device for moving said arm in one direction to first engage one contact and then separate from the other, means pivoted on said switch arm engaging and moving `said movable member as said condition responsive device moves said switch arm in the opposite direction so as to prevent said switch arm from engaging said other contact, and a stationary stop, continued movement of said switch arm in said opposite direction first causing separation oi' said one contact from said switch arm, after which said pivoted means will engage said stop causing said pivoted means to rotate about its pivot and disengage said member permitting said other contact to come into contact with said switch arm.

5. A switching mechanism comprising in combination, a pivotally mounted switch arm, a member mounted for swinging movement, a pair of contacts on said member, means for insulating said contacts with respect to each other, means on said switch arm for cooperation with said contacts, a lever pivoted on said switch arm, means biasing said lever to a position where it will engage said member upon rotation of said switch arm in one direction, and a stop adjacent said lever for causing it to rotate about its pivot on rotation of said switch arm.

6. A switching mechanism comprising in combination, a first switch arm pivotally mounted intermediate its ends, contacts on said switch arm on opposite sides of its pivot, a second switch arm, means connected to one end of said second switch arm for mounting it for rotative movement and for biasing it toward said first switch arm, a pair of contacts on said second switch arm, a condition responsive device for rotating said first switch arm in one direction to cause one of its contacts to engage one of the contacts on said second switch arm, such engagement on further rotation of said first switch arm causing a swinging movement of said second switch arm and a disengagement of the other contacts, a latch on said first switch arm for engaging said second switch arm and swinging it further as said condition responsive device rotates said first switch arm in the opposite direction to cause disengagement of said engaged contacts, and means for tripping said latch to permit engagement of said other contacts upon further rotation of said first switch arm in the opposite direction by said condition responsive device.

7. A switch mechanism comprising a pair of levers, a pair of switch contacts on each lever, the contacts on one lever cooperating with the contacts on the other lever, Vrotation of one lever in one direction causing engagement of one set of contacts which in turn causes disengagement of the other set of contacts, latch means for causing disengagement of said one set of contacts upon rotationfof said one lever in the opposite direction, said latch means preventing engagement of said other set of contacts, and means to trip said latch and permit engagement of said other set of contacts on further rotation of said one lever in said opposite direction.

8. A switch mechanism comprising a pair of levers, a pair of switch contacts on each lever, the contacts onjone lever cooperating with the contacts on the other lever, rotation of one lever in one direction causing engagement of one set of contacts which in turn causes disengagement of the other set of contacts, latch means for causing disengagement of said one set of contacts upon rotation of said one lever in the opposite direction, said latch means preventing engagement of said other set of contacts,v means to trip said latch and permit engagement of said other set of contacts on further rotation of said one lever in said opposite direction, a condition responsive device for rotating said one lever back and forth, stops for limiting the amount of rotation of said one lever, and slip frictionmeans connecting said one lever and said condition responsive device.

9. -In combination, a switch arm, a pair of contacts mounted for cooperation with said switch arm, a condition responsive device for moving said arm in one direction to rst engage one contact and then separate from the other, means on said switch arm causing movement of said other contact to prevent engagement with said switch arm until after the switch arm has separated from said one contact on movement of said switch arm in the opposite direction, stops for limiting the movement of said switch arm, and slip friction means connecting said condition responsive device to said switcharm.

10. In a device of the character described comprising in combination, a switch arm, a movable member, a pair of contacts carried by said movable member, a condition responsive device for moving said arm in one direction to iirst engage one contact and then separate from the other, means on said arm engaging and moving said movable member as said condition responsive device moves said switch arm in the opposite direction soas to prevent said switch arm from engaging said other contact, means for disengaging said iirst mentioned means from said movable member after said switch arm has disengaged said one contact to `permit it to engage said other contact, and means for varying the time between the disengagement of said one contact and the engagement of said other contact by said switch arm.

rst switch, formed by a rst contact on said first member and a iirst contact on said second member, a second switch formed by, a second contact on said rst member and asecond contact on said second member, means for moving said iirst member, means onsaid iirst member for movingsaid second member, stationary element causing said latter means to disengage said second member, :means for adjusting one of said iirst contacts, means for adjusting one of said second contacts, vand means for adjusting said stationary element. 12. In an automatic switching mechanism,

rst switch comprising rst and second contacts, a 'second switch comprising third and fourth contacts, an actuating member for moving said ilrst and second contacts into engagement with each other, and mechanical connecting means by means of which said actuating member separates said third and fourth contacts, said mechanical connecting means including said first and second contacts, whereby the mechanical force for opening said second switch must pass mechanically through said closed rst switch.

13. In an automatic switching mechanism, a i'irst switch comprising rst and second contacts, a second switch comprising third and fourth contacts, an actuating member for moving said first and second contacts into engagement with each other, and mechanical connecting means by means of which said actuating member separates said third and fourth contacts, said mechanical connecting means including said first and second contacts, whereby the mechanical force for opening said second switch must pass mechanically through said closed first switch as said actuating member moves in'one direction, and means preventing the closing of said second switch until after said first switch has been .openedas said 1l. A switching mechanism comprising a first movable member, a second movable member, "a

actuator moves in the Vopposite direction.

l FREDERICK D'. JOES'I'ING.f

LESLIE H. MILLER.. 

